Recently, terrestrial digital radio broadcasting has spread which uses a frequency of an existing AM/FM analog broadcast, and transmits an analog broadcast and a digital signal simultaneously.
In North America, about 1700 or more broadcasting stations have already started or are preparing IBOC (In-Band On Channel) hybrid broadcasting.
Being different from the terrestrial digital radio broadcasting of Japan, since the hybrid broadcasting can utilize the same frequency as that of the existing analog broadcasting, it is not necessary for a broadcasting station to prepare a new frequency for digital broadcasting. Accordingly, a conventional analog radio receiver can receive existing broadcasts, and an HD radio receiver compatible with digital reception can receive a digital radio broadcast. When receiving the digital signal, the HD radio receiver can achieve tone quality equivalent to FM broadcasting as to AM broadcasting, and tone quality equivalent to CD (Compact Disc) as to FM broadcasting.
The HD radio receiver is often provided with a function of successively searching for broadcasting stations with good receiving conditions within a receivable frequency band, and of storing them in a preset memory (referred to as an autostore function from now on). According to the autostore function, it can store broadcasting station data in a preset memory in order of reception quality, and provide a user with the broadcasting station data stored in the preset memory, thereby being able to provide convenience of tuning.
According to the autostore function described above, however, since the receivable broadcasting station data are stored in the order of reception quality, and the HD radio receiver stores data on many analog broadcasting stations, it cannot achieve its original functions sufficiently.
For this reason, a preset method of a receiving set has been conventionally known which detects receiving frequencies of the digital broadcasts and analog broadcasts successively, and registers broadcasting stations relating to the digital broadcasting preferentially (see Patent Document 1, for example).